Multi-stage solids feeder system and method

ABSTRACT

A system includes a multi-stage solids feeder. The multi-stage solids feeder includes a first solids feeder having a first inlet and a first outlet, a second solids feeder having a second inlet and a second outlet, and a conduit disposed between the first outlet and the second inlet. The second solids feeder is disposed adjacent to the first solids feeder, and the conduit routes a solids flow from the first solids feeder to the second solids feeder.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to systems and methods forfeeding solids between upstream and downstream systems.

Solids feeders are used in a variety of industries to transport a solidmaterial. Unfortunately, existing solids feeders generally do notadequately isolate upstream and downstream systems. For example,existing solids feeders are generally ineffective at separating upstreamand downstream atmospheres, which may be at different pressures,compositions, and so forth. Furthermore, separation of upstream anddownstream atmospheres may be difficult with inconsistent materialsupply by the solids feeder, which may be particularly susceptible tovariation in flow rates due to conditions in the upstream or downstreamsystems.

BRIEF DESCRIPTION OF THE INVENTION

Certain embodiments commensurate in scope with the originally claimedinvention are summarized below. These embodiments are not intended tolimit the scope of the claimed invention, but rather these embodimentsare intended only to provide a brief summary of possible forms of theinvention. Indeed, the invention may encompass a variety of forms thatmay be similar to or different from the embodiments set forth below.

In a first embodiment, a system includes a multi-stage solids feeder.The multi-stage solids feeder includes a first solids feeder having afirst inlet and a first outlet, a second solids feeder having a secondinlet and a second outlet, and a conduit disposed between the firstoutlet and the second inlet. The second solids feeder is disposedadjacent to the first solids feeder, and the conduit routes a solidsflow from the first solids feeder to the second solids feeder.

In a second embodiment, a system includes a multi-stage solids feeder,which includes a first solids feeder and a second solids feeder. Thefirst solids feeder includes a first rotary mechanism disposed in afirst chamber between a first inlet and a first outlet. The secondsolids feeder includes a second rotary mechanism disposed in a secondchamber between a second inlet and a second outlet. The first and secondsolids feeders are disposed adjacent one another, the first outlet iscoupled to the second inlet, and the multi-stage solids feeder isconfigured to substantially block gas flow while enabling a solids flow

In a third embodiment, a method includes feeding a solids flow through afirst solids feeder from a first inlet, along a first rotary mechanismwithin a first chamber, and out through a first outlet. The method alsoincludes feeding the solids flow from the first outlet through a secondsolids feeder from a second inlet, along a second rotary mechanismwithin a second chamber, and out through a second outlet. The first andsecond solids feeders are disposed adjacent one another as a multi-stagefeeder. In addition, the method includes creating at least one dynamicplug of the solids flow in the multi-stage feeder to substantially blockgas flow while enabling the solids flow through the multi-stage feeder.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of an embodiment of a system having amulti-stage solids feeder;

FIG. 2 is a cross-sectional side view of an embodiment of themulti-stage solids feeder of FIG. 1; and

FIG. 3 is a cross-sectional side view of an embodiment of themulti-stage solids feeder of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

Present embodiments are directed to a multi-stage solids feeder used fordepressurizing or metering a solids flow between systems operating atdifferent atmospheric conditions (e.g., different pressures, gascompositions, etc.). The multi-stage solids feeder includes a firstsolids feeder and a second solids feeder configured to feed the solidsflow from an upstream system to a downstream system. The multi-stagesolids feeder creates one or more dynamic plugs of the solids flow tosubstantially block gas flow, while maintaining the solids flow throughthe multi-stage solids feeder. The dynamic plugs may be formed in theentrance or exit of one or both of the solids feeders by the lockup ofsolids within one or both feeders (e.g., locking up while moving), whichmay be positive displacement pumps. The first and second solids feedersmay be disposed adjacent to one another and coupled together via aconduit. The multi-stage solids feeder may include a controller forcontrolling a first and second solid feed rate of the first solidsfeeder and the second solids feeder to maintain the one or more dynamicplugs formed by the solids flow through the multi-stage solids feeder.

Turning now to the drawings, FIG. 1 illustrates a block diagram of anembodiment of a system 10 having a multi-stage solids feeder 12. Theillustrated multi-stage solids feeder 12 includes, among other things, afirst solids feeder 14, a second solids feeder 16, and a conduit 18. Thefirst and second solids feeders 14 and 16 are disposed adjacent to eachother and coupled via the conduit 18. Although the illustratedembodiment includes only the first and second solids feeders 14 and 16,other embodiments of the multi-stage solids feeder 12 may include agreater number of solids feeders (e.g., 3, 4, 5, 6, 7, 8, 9, 10, ormore) coupled in series with conduits between adjacent inlets andoutlets.

The first solids feeder 14 is coupled to an upstream system 20 (e.g.,gasifier). As described herein, the term upstream may be a directiontowards the source of a solids flow 22 (e.g., a low of solidparticulate), while downstream may be in a direction of the solids flow22 passing through the system 10. The first solids feeder 14 isconfigured to receive the solids flow 22 at a first inlet 24. The solidsflow 22 may have various compositions including, but not limited to,fuels (e.g., coal), slag mixtures, dry char, catalysts, plastics,chemicals, minerals, pharmaceuticals, and/or food products. The firstsolids feeder 14 conveys the solids flow 22 from the first inlet 24 to afirst outlet 26 coupled to the conduit 18. The conduit 18 routes thesolids flow 22 from the first solids feeder 14 to a second inlet 28 ofthe second solids feeder 16. Some embodiments may include the first andsecond solids feeders 14 and 16 without the conduit 18 connecting thefirst outlet 26 to the second inlet 28. In such embodiments, the firstoutlet 26 of the first solids feeder 14 is also the second inlet 28 ofthe second solids feeder 16, and the solids flow 22 is fed from thefirst solids feeder 14 directly into the second solids feeder 16.

The second solids feeder 16 directs the feedstock through a secondoutlet 30 of the second solids feeder 16 to a downstream system 32. Insome embodiments, the solids flow 22 is a solid fuel flow (e.g.,particulate coal) directed from the upstream system 20 to the downstreamsystem 32. In other embodiments, however, the system 10 may be agasification system, in which the solids flow 22 conveyed by the firstand second solids feeders 14 and 16 is a slag mixture (e.g., slag andwater) output from a gasifier, as the upstream system 20. As discussedin detail below, the multi-stage solids feeder 12 may allow theformation of at least one dynamic plug of the solids flow 22 in order tosubstantially block gas flow while enabling the solids flow 22 betweenthe upstream system 20 and the downstream system 32. As a result, themulti-stage solids feeder 12 may convey the solids flow 22 from theupstream system 20 at a first atmosphere to the downstream system 32 ata second atmosphere, wherein the first and second atmospheres may havedifferent pressures, different gas compositions, and so forth. This maybe desirable for pressure letdown applications, pressurizingapplications, or for feeding the solids flow 22 at a desired flow ratebetween two incompatible atmospheres.

The multi-stage solids feeder 12 may include a controller 34 configuredto monitor and control the operation of the entire system 10, orcomponents of the system 10, through signal lines 36 and control lines38. In some embodiments, one or more sensors 40 may transmit feedbackfrom components of the system 10 to the controller 34 through signallines 36. The sensors 40 may detect or measure a variety of system andsolids flow properties. The sensors 40 may include but are not limitedto flow sensors, pressure sensors, position sensors, torque sensors,temperature sensors, power sensors, speed sensors, or combinationsthereof. For example, the sensors 40 of the first and second solidsfeeders 14 and 16 may measure the respective first and second solid feedrates, and the sensors 40 of the upstream system 20, the downstreamsystem 32, and the conduit 18 may measure pressure. In particular, thesensor 40 of the upstream system 20 may measure a first pressureupstream of the multi-stage solids feeder 12, the sensor 40 of theconduit 18 may measure a second pressure between the first and secondsolids feeders 14 and 16, and the sensor 40 of the downstream system 32may measure a third pressure downstream of the multi-stage solids feeder12.

The controller 34 may control the operation of the components of thesystem 10 by controlling drive motors 42. Drive motors 42 may drive oractuate the components according to control signals sent via the controllines 38. In an exemplary embodiment, each drive motor 42 for the firstand second solids feeders 14 and 16 may be an electric or hydraulicmotor that drives a positive displacement pump. In some embodiments, thefirst and second solids feeders 14 and 16 may have a common drive motor42. The controller 34 may control the operation of the first and secondfeeders 14 and 16 by adjusting the speed and/or torque of the one ormore drive motors 42. The controller 34 may control components of thesystem 10 based on sensor feedback from the one or more sensors 40. Forexample, the controller 34 may decrease the first feed rate of the firstsolids feeder 14 when the rate of the solids flow 22 entering the firstinlet 24 decreases in order to maintain a dynamic plug of the solidsflow 22 in the first inlet 24, thereby substantially blocking gas flowbetween the upstream system 20 and the first solids feeder 14.Simultaneously, the controller 34 may adjust the second feed rate of thesecond solids feeder 16 in the same manner, in order to maintain adynamic plug of the solids flow 22 entering the second inlet 28 of thesecond solids feeder 16. In general, the first and second solids feeders14 and 16 are maintained at the same solid feed rate by the controller34. Any desired changes in the feed rates, however, may be sequenced sothat a dynamic plug is maintained between the solids feeders 14 and 16.That is, the first feed rate of the first solids feeder 14 may beincreased a desired number of seconds before the second feed rate of thesecond solids feeder 16 is increased so that an undesirable amount ofgas does not leak from the first solids feeder 14 into the second solidsfeeder 16. As the solids flow 22 passes through the conduit 18 betweenthe first and second solids feeders 14 and 16, any high pressure gasthat leaks through the first solids feeder 14 into the conduit 18 may beblocked by the dynamic plug of the solids flow 22 formed upstream of thesecond solids feeder 16. The first and second solids feeders 14 and 16,the conduit 18, the controller 34, the sensors 40, and the drive motors42 may all be part of the multi-stage solids feeder 12.

The controller 34 may be coupled to an operator interface 44 configuredto receive operator input. Through the operator interface 44, anoperator may configure the controller 34 to control how the multi-stagesolids feeder 12 conveys the solids flow 22 to the downstream system 32.Operator input received through the operator interface 44 may defineacceptable variations in the feed rate to the downstream system 32,maximum feed rates or operating speeds, minimum feed rates or operatingspeeds, pressure parameters, or combinations thereof. For example, theoperator may configure the multi-stage solids feeder 12 to convey thesolids flow 22 to the downstream system 32 within approximately 1%, 5%or 10% of a desired feed rate. In some embodiments, the operatorinterface 44 may enable direct control of the system 10 by the operator.Inputs received through the operator interface 44 may direct thecontroller 34 to adjust the solid feed rates of the first and secondsolids feeders 14 and 16 due to a scheduled interruption (e.g.,transition) in the solids flow 22 supplied to the first solids feeder 14by the upstream system 20. This may allow the system 10 to maintain oneor more dynamic plugs of the solids flow 22 through the multi-stagesolids feeder 12. The operator interface 44 may also display information(e.g., sensor feedback) regarding the operation of the system 10 and/orthe multi-stage solids feeder 12.

Some embodiments of the system 10 include a gasification system.Gasification technology can convert hydrocarbon feedstocks, such ascoal, biomass, and other carbonaceous feed sources, into a gaseousmixture of carbon monoxide (CO) and hydrogen (H₂), i.e., syngas, byreaction with oxygen and steam in a gasifier. These gases may beprocessed and utilized as fuel, as a source of starting materials formore complex chemicals, for the production of substitute natural gas, ora combination thereof. In some embodiments, the upstream system 20 maybe a gasifier that supplies the solids flow 22 (e.g., dry char or slagmixture) to the first solids feeder 14. The upstream system 20 maycondition the solids flow 22 for input into the multi-stage solidsfeeder 12 and the downstream system 32. To allow this conditioning, theupstream and downstream systems 20 and 32 may be controlled by thecontroller 34. As described in detail below, the first and second solidsfeeders 14 and 16 may be positive displacement pumps. The second solidsfeeder 16 conveys the solids flow 22 to the downstream system 32, whichmay include a slag handling unit, a gas turbine, a generator, a reactor,a combustor, a boiler, a furnace, and so forth.

Presently contemplated embodiments of the multi-stage solids feeder 12may feed the solids flow 22 from the upstream system 20 operating at afirst atmosphere to the downstream system 32 operating at a secondatmosphere. More specifically, the upstream and downstream systems 20and 32 may be operating at different pressures and/or gas compositions.For example, the upstream system 20 may be a gasifier supplying thesolids flow 22 (e.g., dry char or slag mixture) to the multi-stagesolids feeder 12 at a relatively high pressure. The downstream system 32may operate at lower pressures than at least the first solids feeder 14and the upstream system 20. In other embodiments, the multi-stage solidsfeeder 12 may feed the solids flow 22 at a relatively uniform flow ratebetween two incompatible atmospheres. It may be undesirable for theupstream and downstream atmospheres to mix, or for a relatively higherpressure gas to flow through the multi-stage solids feeder 12.Therefore, the multi-stage solids feeder 12 may be configured tosubstantially block gas flow while enabling the solids flow 22 to passbetween the upstream and downstream systems 20 and 32. In order toaccomplish this, the multi-stage solids feeder 12 may maintain at leastone dynamic plug of the solids flow 22 to block gas flow, as describedin detail below. Dynamic plugs may be formed as a result of lockup ofthe solids flow 22 moving through the multi-stage solids feeder 12. Thepressure of the solids lockup may be high enough to form a pressure sealthat substantially reduces, and in some cases completely prevents, thepassage of gas through the dynamic plug. The multi-stage solids feedermay include one or more buffer gas supplies (not shown) to introduce aninert buffer gas to certain locations in the multi-stage solids feeder12. The buffer gas may substantially block gases from leaking throughthe dynamic plug of solids flowing through the multi-stage solids feeder12. The multiple dynamic plugs in the multi-stage solids feeder 12 maydecrease the amount of high pressure gas from the upstream system 20that flows to the second solids feeder 16 and/or the downstream system32. Similarly, the dynamic plugs may decrease the amount of gas flowingfrom the downstream system 32 to the first solids feeder 14 and/or theupstream system 20. The controller 34 may adjust the first or secondsolid feed rates of the first and second solids feeders 14 and 16 tomaintain the desired dynamic plugs in the multi-stage solids feeder 12.

FIG. 2 is a cross-sectional side view of an embodiment of themulti-stage solids feeder 12 of FIG. 1. Each of the first and secondsolids feeders 14 and 16 may include a rotary mechanism disposed in achamber and used to move the solids flow 22 from an inlet to an outletof the feeder. In some embodiments, the rotary mechanism may include arotor that directly moves the solid particles from the inlet to theoutlet of the solids feeder. In other embodiments, the rotary mechanismmay include a conveyor belt that is disposed about one or more rotors.As the rotors of the conveyor belt rotate, the conveyor moves the solidparticles through the solids feeder, from the inlet to the outlet. Thedisclosed techniques may be applied using either of theseconfigurations, or any type of solids feeder having a rotary mechanismdisposed in a chamber for moving the solids flow 22. In eitherconfiguration, the solids flow 22 may be moved through the solidsfeeders 14 and 16 in a solids lockup condition, and the multi-stagesolids feeder 12 may create one or more dynamic plugs upstream and/ordownstream of the solids feeders 14 and 16.

In the illustrated embodiment, the first solids feeder 14 of themulti-stage solids feeder 12 is a first positive displacement pump 60.The second solids feeder 16 is a second positive displacement pump 62.One or both of the positive displacement pumps 60 and 62 may be aPOSIMETRIC® Feeder made by General Electric Company of Schenectady, NewYork. As shown in FIG. 2, the first positive displacement pump 60 mayinclude a first rotor 64 disposed in a first chamber 66 between thefirst inlet 24 and the first outlet 26. Similarly, the second positivedisplacement pump 62 may include a second rotor 68 disposed in a secondchamber 70 between the second inlet 28 and the second outlet 30. Each ofthe first and second rotors 64 and 68 include two substantially opposedand parallel rotary discs 72, which may include discrete cavitiesdefined by protrusions 74 to drive the solids flow 22 therebetween,creating a solids lockup condition, as described below. The rotary discs72 of the first rotor 64 may be movable relative to the first chamber 66in a rotational direction 76 from the first inlet 24 towards the firstoutlet 26. Likewise, the rotary discs 72 of the second rotor 68 may bemovable relative to the second chamber 70 in a rotational direction 78from the second inlet 28 to the second outlet 30. In the illustratedembodiment, the rotors 64 and 68 are configured to rotate in the samerotational directions 76 and 78. As discussed previously, themulti-stage solids feeder 12 is configured to substantially block gasflow through the multi-stage solids feeder 12 while enabling the solidsflow 22 to move from the upstream system 20 to the downstream system 32.

As noted above, each of the first and second rotors 64 and 68 includetwo substantially opposed and parallel rotary discs 72, separated by ahub 79 and joined to a shaft that is common to the rotary discs 72 andthe hub 79. In the first positive displacement pump 60, a convex surfaceof the hub 79, annular portions of both rotary disks 72 extendingbetween the hub 79 and the outer circumference of the rotary discs 72,and an inner surface of the first chamber 66 define an annularly shaped,rotating channel that connects the first inlet 24 and the first outlet26. A portion of the first chamber 66 disposed between the first inlet24 and the first outlet 26 divides the rotating channel in such a waythat solids entering the first inlet 24 may travel only in a directionof rotation 76 of the first rotor 64, so that the solids may be carriedfrom the first inlet 24 to the first outlet 26 by means of the rotatingchannel.

As the solids flow 22 enters and moves through the first inlet 24, thesolid particles progressively compact. As the solid particles continueto be drawn into the rotating channel, the compaction may reach a pointwhere the particles become interlocked and form a bridge across theentire cross-section of the rotating channel. As the compacted particlescontinue to move through the rotating channel in the direction ofrotation 76, the length of the zone containing particles which haveformed an interlocking bridge across the entire cross-section of therotating channel may become long enough that the force required todislodge the bridged particles from the rotating channel exceeds theforce that may be generated by the pressure the first outlet 26. Thiscondition, where the interlocking solids within the rotating channelcannot be dislodged by the pressure at the first outlet 26, is called“lockup”. By achieving the condition of lockup, the torque delivered bythe shaft from the drive motor 42 may be transferred to the rotatingsolids so that the solids are driven from the first inlet 24 to thefirst outlet 26 against whatever pressure exists in the environmentbeyond the first outlet 26. In some embodiments, the rotary discs 72 mayhave raised or depressed surface features 74 formed onto their surfaces.These features 74 may enhance the ability of the particulate solids toachieve lockup in the rotating channel and, therefore, may enhance theability of the drive shaft to transfer torque to the rotating solids.The components of the second positive displacement pump 62 operate inthe same way to convey the solids flow 22 through an annular rotatingchannel of the second rotor 68 in a rotational direction 78.

Upon entering through an opening 80 of the first inlet 24, the solidsflow 22 may travel in a direction 82 from the first inlet 24 to thefirst outlet 26. The solids flow 22 is moved through the first positivedisplacement pump 60 in the solids lockup condition as the rotary discs72 rotate, and exits the first positive displacement pump 60 through thefirst outlet 26. From here, the solids flow 22 continues through theconduit 18 in a direction 84 from the first outlet 26 of the firstpositive displacement pump 60 to the second inlet 28 of the secondpositive displacement pump 62. As the solids flow 22 enters the secondinlet 28, the solids flow 22 travels in a direction 86 from the secondinlet 28 to the second outlet 30. The solids flow 22 is moved throughthe second positive displacement pump 62 in the solids lockup conditionas the rotary discs 72 rotate, and exits the second positivedisplacement pump 62 through the second outlet 30. The solids flow 22 isfinally fed through an opening 88 of the second outlet 30 to thedownstream system 32.

The multi-stage solids feeder 12 is designed to feed the solids flow 22from the upstream system 20 to the downstream system 32. The upstreamsystem 20 may operate at a first atmosphere and the downstream system 32may operate at a second atmosphere, where the first and secondatmospheres have different pressures and/or different gas compositions.In order to feed the solids flow 22 from the upstream system 20 at thefirst atmosphere to the downstream system 32 at the second atmosphere,the multi-stage solids feeder 12 may allow the solids flow 22 whilereducing a gas flow therethrough. To do so, the multi-stage solidsfeeder 12 may maintain at least one dynamic plug of the solids flow 22through the multi-stage solids feeder 12. Such dynamic plugs, formed bythe solids flow 22 locking up in the positive displacement pumps 60 and62, may divide the multi-stage solids feeder 12 into componentsoperating at different pressures. Such components may include a firstseal duct 90 between the opening 80 and the first inlet 24, the firstpositive displacement pump 60, a second seal duct 92 (e.g., the conduit18), the second positive displacement pump 62, and a third seal duct 94between the second outlet 30 and the opening 88. Each of thesecomponents may operate at different pressures while feeding the solidsflow 22 between the upstream and downstream systems 20 and 32.

The multi-stage solids feeder 12 having two solids feeders may createdynamic plugs of the solids flow 22 in as few as one and up to three ofthe seal ducts 90, 92, and 94. For example, the illustrated embodimentshows a first dynamic plug 96 in the first seal duct 90, a seconddynamic plug 98 in the second seal duct 92, and a third dynamic plug 100in the third seal duct 94. In the illustrated embodiment, the first,second, and third dynamic plugs 96, 98, and 100 are represented bydashed lines. The first dynamic plug 96 may be formed by a lockup of thesolids flow 22 entering the first positive displacement pump 60. Sincethe solids flow 22 rotates through the first positive displacement pump60 in a solids lockup condition, the solids flow 22 entering the firstseal duct 90 may build up to form the first dynamic plug 96. The firstdynamic plug 96 may allow the solids flow 22 to enter the first positivedisplacement pump 60 while blocking the flow of gas from the upstreamsystem 20 into the first positive displacement pump 60. Maintaining thefirst dynamic plug 96 may allow the pressure in the first seal duct 90(which is approximately the same as the pressure of the upstream system20) to be different than the pressure in the first positive displacementpump 60. The multi-stage solids feeder 12 may be coupled to a buffer gassupply 102. The buffer gas supply 102 provides an inert buffer gas, suchas nitrogen, into a flow path through the multi-stage solids feeder 12.In the illustrated embodiment, the buffer gas supply 102 provides thebuffer gas to the first seal duct 90 through a gas inlet 104 locatedupstream of the first inlet 24. The buffer gas acts as an additionalbarrier to gases entering the first seal duct 90 from the upstreamsystem 20 while allowing the solids flow 22 to pass. The buffer gassupply 102 may be especially useful for separating a solid/gas mixtureoutput by the upstream system 20 into a gas and the solids flow 22. Thegas may then be directed toward a different application (e.g., gasturbine engine) and the solids flow 22 may continue through themulti-stage solids feeder 12 toward the downstream system 32.

The multi-stage solids feeder 12 may create the second dynamic plug 98of the solids flow 22 at the first outlet 26, the conduit 18, or thesecond inlet 28, or any combination thereof. The second dynamic plug 98is formed by the solids flow 22 locking up as it enters the secondpositive displacement pump 62. As long as the second dynamic plug 98 ismaintained within the second seal duct 92, the first and second positivedisplacement pumps 60 and 62 may operate at different pressures. It maybe desirable for the solids feeders 14 and 16 to be located relativelynear each other, so that the conduit 18 between the first outlet 26 andthe second inlet 28 may be short enough to maintain the second dynamicplug 98. In some embodiments, the second seal duct 92 may be shaped suchthat the second dynamic plug 98 is maintained at a particular point inthe conduit 18. In this way, the second dynamic plug 98 may bemaintained in the middle of the conduit 18, toward the first outlet 26,or toward the second inlet 28, as illustrated. In addition, themulti-stage solids feeder 12 may be dimensioned such that the conduit 18is not too long to maintain the lockup condition for forming the seconddynamic plug 98.

The third dynamic plug 100 may be formed by a lockup of the solids flow22 exiting the second positive displacement pump 62. In the illustratedembodiment, the third dynamic plug 100 is maintained passively since thethird seal duct 94 has an upward slope. Other embodiments may include avalve or specially shaped third seal duct 94 to actively maintain thethird dynamic plug 100. For example, there may be a turn in the thirdseal duct 94 for maintaining a plug of the solids flow 22 exiting thesecond positive displacement pump 62.

The multi-stage solids feeder 12 may create one or more of the dynamicplugs 96, 98, or 100. The dynamic plugs 96, 98, and 100 are configuredto block gas flow using the solids flow 22, thereby enabling componentsof the multi-stage solids feeder 12 on either side of each dynamic plugto operate at different pressures. For example, the first dynamic plug96 may separate gas at a first pressure in the first seal duct 90 fromgas at a second pressure in the second seal duct 92. The first positivedisplacement pump 60 may operate at a pressure that is different fromthe first and/or second pressures. The first positive displacement pump60 may include a vent 106 for removing gas 108 from the first positivedisplacement pump 60 and, consequently, reducing a first pump pressure.Similarly, the third dynamic plug 100 may separate gas at the secondpressure in the second seal duct 92 from gas at a third pressure in thethird seal duct 94. The second positive displacement pump 62 may operateat a pressure that is different from the second and/or third pressures.The second positive displacement pump 62 may include a vent 110 forremoving gas 112 from the second positive displacement pump 62 and,consequently, reducing a second pump pressure. It should be noted thatvents throughout the multi-stage feeder 12, which may include the firstand second vents 106 and 110, can help to remove any gas leakage betweenthe upstream and downstream systems 20 and 32.

The controller 34 may control the first solid feed rate of the firstsolids feeder 14 and/or the second solid feed rate of the second solidsfeeder 16 to maintain the desired dynamic plugs within the multi-stagesolids feeder 12. For example, the controller 34 may decrease the firstsolid feed rate of the first positive displacement pump 60 to maintainthe first dynamic plug 96 in the first seal duct 90. It should be notedthat the controller 34 decreases the second solid feed rate by the sameamount, in order to keep the first and second positive displacementpumps 60 and 62 synchronized, thereby maintaining the second dynamicplug 98 and/or third dynamic plug 100. The controller 34 may respond tosensor feedback indicative of the first pressure upstream of themulti-stage solids feeder 12 (e.g., in the first seal duct 90) or asolid feed rate of the solids flow 22 entering the first seal duct 90.If the solid feed rate is not high enough to maintain effective lockupof the solids flow 22 at the first inlet 24, the controller 34 mayoperate the first positive displacement pump 60 at a lower solid feedrate to maintain the first dynamic plug 96. In addition, if the pressuremeasured in the first positive displacement pump 60 approaches the firstpressure in the first seal duct 90, the controller 34 may operate thefirst positive displacement pump 60 at a lower solid feed rate tomaintain the first dynamic plug 96. A low solid feed rate of the solidsflow 22 entering the multi-stage solids feeder 12 may result in a lossof the first dynamic plug 96 until the controller 34 performs anappropriate adjustment of the first solid feed rate. In such instances,gas that leaks into the first positive displacement pump 60 from thefirst seal duct 90 may exit the pump through the vent 106. Any remaininggas in the first positive displacement pump 60 may be blocked by thesecond dynamic plug 98 and/or the third dynamic plug 100. Thus, themultiple solids feeders 14 and 16 in series may add redundancy to theblockage of gas flow through the multi-stage solids feeder 12, from theupstream system 20 to the downstream system 32 or vice versa.

It may be desirable for the controller 34 to operate the second solidsfeeder 16 at a lower solid feed rate than the first solids feeder 14 inorder to maintain the second dynamic plug 98 between the two solidsfeeders 14 and 16. This operation of the solids feeders 14 and 16 atdifferent feed rates would be performed just long enough for the solidsfeeders 14 and 16 to be resynchronized and the second dynamic plug 98reestablished. In general, the second solids feeder 16 may act as abrake for the first solids feeder 14 in the event that the seconddynamic plug 98 is lost, which could otherwise lead to loss of pressurecontainment. Maintaining the third dynamic plug 100 through propershaping and/or orientation of the third seal duct 94 or through anactive control mechanism (e.g., a valve) may block gases from flowingbetween the second positive displacement pump 62 and the downstreamsystem 32, in either direction. This may be especially important inapplications where the second positive displacement pump 62 operates ata lower pressure than the downstream system 32. Any undesirable gas thatenters the second positive displacement pump through the second sealduct 92 or through the third seal duct 94 may exit the second positivedisplacement pump 62 through the vent 110.

The multi-stage solids feeder 12 may be used in different applicationsfor feeding the solids flow 22 between upstream and downstream systemsat different atmospheres, including pressure letdown operations. Onesuch application includes the removal of dry char from a high pressuresyngas atmosphere. In this type of operation, the solids flow 22 is adry char that forms part of an untreated syngas output from the upstreamsystem 20 (e.g., gasifier). The multi-stage solids feeder 12 may removethe dry char from the syngas so that the syngas can be further treatedand used for power generation, chemical production, or anotherdownstream process. The dry char is removed to ambient air, so themulti-stage solids feeder 12 uses dynamic seals to depressurize theincoming solids flow 22 (dry char) before outputting the solids flow 22to the downstream system 32. In this application, the first dynamic plug96 is operating passively in the inlet of the first seal duct 90,meaning that though the first dynamic plug 96 forms and the solids flow22 locks up within the first positive displacement pump 60, there is nosignificant change in operating pressure across the first dynamic plug96. Consequently, the first pressure in the first seal duct 90 and thepressure in the first positive displacement pump 60 may be approximatelyequal to the gasifier pressure of the upstream system 20. The seconddynamic plug 98 is a pressure reducing plug in the second seal duct 92,meaning that the solids flow 22 forms a plug at the second inlet 28across a pressure difference between the first and second positivedisplacement pumps 60 and 62 utilizing the lockup of the solids flow 22within the second positive displacement pump 62. Consequently, thesecond dynamic plug 98 reduces the pressure of the solids flow 22through the multi-stage solids feeder 12. The second positivedisplacement pump 62 may operate at a pressure between the operatingpressures of the first positive displacement pump 60 and the downstreamsystem 32, or at a pressure lower than the atmospheric pressure of thedownstream system 32. The buffer gas supply 102 may introduce a nitrogenbuffer gas upstream of the first dynamic plug 96 in the first seal duct90. The buffer gas may provide an inert barrier between the syngas andthe first positive displacement pump 60, helping to strip the solidsflow 22 of the syngas as the solids flow 22 enters the first inlet 24.Any gas that leaks through the solids flow 22 into the first inlet 24 ofthe multi-stage solids feeder 12 may be removed through the vents 106and 110. The second vent 110 may regulate the relatively lower pressurewithin the second positive displacement pump 62. Some embodiments of themulti-stage solids feeder 12 may maintain the third dynamic plug 100 forchar removal applications, while others may not.

It should be noted that in other embodiments, the buffer gas supply 102may be introduced at different positions of the multi-stage solidsfeeder 12. For example, the buffer gas supply 102 may be introduced intothe second or third seal ducts 92 and 94 as well. Although only one isshown, there may be multiples buffer gas supplies 102 throughout themulti-stage solids feeder 12. Indeed, there may be one in each of thedifferent seal ducts 90, 92, and 94 to reduce an amount of undesirablegas leaking between the upstream system 20, downstream system 32, andthe solids feeders 14 and 16.

The multi-stage solids feeder 12 may also be useful in applicationsinvolving metering a solids flow 22 between two incompatibleatmospheres, which may or may not be at different pressures. That is,the pressure of the upstream system 20 may be approximately the same,slightly higher, or slightly lower than the pressure of the downstreamsystem 32. The multi-stage solids feeder 12 may operate similarly to themulti-stage solids feeder 12 used for depressurization, as describedabove. To block the flow of higher pressure gas from the downstreamsystem 32 into the multi-stage solids feeder 12, the multi-stage solidsfeeder 12 may include an additional buffer gas supply coupled to thethird seal duct 94 downstream of the third dynamic plug 100. In otherembodiments, the multi-stage solids feeder 12 may maintain the first andthird dynamic plugs 96 and 100 in the first and third seal ducts 90 and94, respectively, without forming a second dynamic plug 98 in the secondseal duct 92. In this case, the third seal duct 94 may be appropriatelyshaped (e.g., oriented upward, bent, or curved) or include an activecontrol mechanism (e.g., valve) toward the opening 88 for maintainingthe third dynamic plug 100.

The multi-stage solids feeder 12 also may be useful for continuous slagremoval from a gasifier. In addition to syngas, the gasifier generates aslag mixture byproduct, which may be a wet ash material. It may bedesirable for the multi-stage solids feeder 12 to feed the slag mixturefrom the upstream system 20 (e.g., a quench chamber of the gasifier) tothe downstream system (e.g., a slag handling unit). The slag mixture maybe a mixture of slag and water, the slag forming the solids flow 22. Thesolid/liquid slag mixture may flow through the multi-stage solids feeder12, however, as long as the dynamic plugs and lockup condition of thesolids flow 22 are maintained. The multi-stage solids feeder 12 may feedthe solids flow 22 and the water of the slag mixture through themulti-stage solids feeder 12 without permitting gas flow through themulti-stage solids feeder 12. In some embodiments, the upstream system20 may include a liquid removal section for removing the liquid waterfrom the slag mixture before the slag enters the multi-stage solidsfeeder 12. The solids flow 22 may be pressurized as it exits the highpressure gasifier, and the downstream system 32 may include a slaghandling unit or conveyor system that operates at ambient airconditions. Thus, the multi-stage solids feeder 12 may depressurize thesolids flow 22 of the slag mixture as it flows through the multi-stagesolids feeder 12. The pressure drop of the solids flow 22 may occurprimarily across the second seal duct 92, or across a combination of thefirst, second, and third seal ducts 90, 92, and 94. Some embodiments mayinclude a supply of flush water supplied to the solids flow 22 upstreamof the first seal duct 90 in order to wash and cool the slag mixture asit exits the upstream system 20. A certain amount of dewatering of theslag mixture may occur as the solids flow 22 moves through themulti-stage solids feeder 12. Specifically, the multi-stage solidsfeeder 12 may be designed such that a desired amount of water is removedfrom the solids flow 22 through the vents 106 and 110 of the multi-stagesolids feeder 12.

It should be noted that presently contemplated embodiments are notlimited to use in the solid feeding applications described in detailabove. The multi-stage solids feeder 12 may be used for any otheroperations where depressurization of a solids flow 22 is desired. Themulti-stage solids feeder 12 also may be used for other operationsrelated to conveying a solids flow 22 between two incompatibleatmospheres.

FIG. 3 is a cross-sectional side view of another embodiment of themulti-stage solids feeder 12 having two positive displacement pumps 60and 62 in series. In this embodiment, the rotors 64 and 68 areconfigured to rotate in opposite rotational directions 76 and 78. Themulti-stage solids feeder 12 includes the first, second, and third sealducts 90, 92, and 94, where the solids flow 22 may lock up to maintainone or more of the dynamic plugs 96, 98, or 100. In the illustration,the second positive displacement pump 62 outputs the solids flow 22 in adownward direction toward the downstream system 32. In thisconfiguration, the multi-stage solids feeder 12 includes a valve 130that may be opened or closed to establish the third dynamic plug 100downstream of the second outlet 30. In some embodiments, the valve 130may be a solenoid valve, ball valve, gate valve, rotor valve,continuously variable valve, or the like, and may be continuouslypositioned between a fully open and fully closed position. The valve 130may be controlled by electromechanical actuators, pneumatic actuators,hydraulic actuators, or other suitable controls. The controller 34 mayactively control the position of the valve 130 to allow the solids flow22 to pass through the third seal duct 94 while maintaining the thirddynamic plug 100.

The controller 34 may independently control the first and second rotors64 and 68. As a result, the multi-stage solids feeder 12 may provide adesired output of the solids flow 22 while maintaining a relativelyconstant load on the solids flow 22 moving through the second seal duct92. The second rotor 68 effectively acts as a brake to maintain thesecond dynamic plug 98 while also moving the solids flow 22 toward thedownstream system 32. For example, the controller 34 may adjust thesecond solid feed rate of the second solids feeder 16 for a desiredoutput feed rate. Simultaneously, the controller 34 may adjust the firstsolid feed rate of the first solids feeder 14 to control a torque, load,a pressure drop, or volume of voids of the solids flow 22 in one or bothof the solids feeders 14 and 16. The valve 130 may be operated tomaintain a minimum force of the solids flow 22 exiting the multi-stagesolids feeder 12, maintaining the third dynamic plug 100 of the solidsflow 22.

It should be noted that the multi-stage solids feeder 12 includes atleast the two solids feeders 14 and 16 coupled in series and locatedadjacent to one another. The solids feeders 14 and 16 are connected suchthat the solids flow 22 may continue from the first outlet 26 to thesecond inlet 28. As previously mentioned with respect to FIG. 2, it maybe desirable for the solids feeders 14 and 16 to be located relativelynear each other, so that the conduit 18 between the first outlet 26 andthe second inlet 28 may be short enough to maintain the second dynamicplug 98. If the conduit 18 is too long, the solids flow 22 exiting thefirst solids feeder 14 may produce excessive torque, exceeding thecapability for the solids flow 22 to lock up in the solids feeder 12 andmaintain the second dynamic plug 98. To prevent this, the multi-stagesolids feeder 12 may be properly dimensioned to maintain the desiredsecond dynamic plug 98 based on expected feed rates, pressures, pumpcharacteristics, and feeder applications (e.g., depressurization ormetering). The multi-stage solids feeder 12 may include a minimum lineardimension 132 representative of the minimum linear distance between thefirst and second solids feeders 14 and 16. The multi-stage solids feeder12 may have the solids feeders 14 and 16 spaced to maintain a desiredratio of the minimum linear dimension 132 to a maximum feeder dimension134 (e.g., pump diameter) of the first and second solids feeders 14 and16. The ratio of the minimum linear dimension 132 to the maximum feederdimension 134 may be less than approximately 0.2, 0.4, 0.5, 0.8, or 1.0,within a desired range of approximately 0 to 1.0, 0.2 to 0.8, 0.4 to0.75, or 0.3 to 0.5, or any ratio suitable to maintain the seconddynamic plug 98. This way, the solids flow 22 may maintain a pressurebetween the first outlet 26 and the second inlet 28 for establishing andmaintaining the second dynamic plug 98. In some embodiments, themulti-stage solids feeder 12 may be operated at such feed rates andunder conditions where a conduit 18 is not desired and the first outlet26 is immediately adjacent to the second inlet 28.

The multi-stage solids feeder 12 may be arranged and operated indifferent ways depending on desired operating parameters such as solidfeed rates, solids feeder dimensions, pressure distributions, solidsflow compositions, and control operations. If the first and secondsolids feeders 14 and 16 are positive displacement pumps 60 and 62, asillustrated, the positive displacement pumps 60 and 62 may be positionedat different orientations relative to each other. For example, thepositive displacement pumps 60 and 62 may be positioned in a verticalorientation (e.g., the first positive displacement pump 60 above orbelow the second positive displacement pump 62). The positivedisplacement pumps 60 and 62 may have their respective inlets 24 and 28and outlets 26 and 30 located in different circumferential positionsrelative to the rotors 64 and 68. This is shown in the differentarrangements of FIGS. 2 and 3. In other embodiments, the seal ducts 90,92, or 94 may be positioned at different relative angles between thefirst and second positive displacement pumps 60 and 62. Differentalignments of the positive displacement pumps 60 and 62 and the conduit18 can modify the seal ducts 90, 92, and 94 as well as the positionwithin each seal duct where the solids lockup occurs. As previouslydiscussed, the positive displacement pumps 60 and 62 may be rotated inthe same direction (FIG. 2) or in opposite directions (FIG. 3). Thepositive displacement pumps 60 and 62 may be driven together orseparately. In some embodiments, the rotors 64 and 68 may be gearedtogether and driven by the same motor drive. Other embodiments may usetwo separate drives to enable independent control of the positivedisplacement pumps 60 and 62. Still other embodiments may use one driveto rotate both rotors 64 and 68, this drive being coupled with eachrotor via an adjustable gear reduction, so that the controller 34 maycontrol the feed rate of each positive displacement pump 60 and 62.

In some embodiments, the conduit 18 between the first and second solidsfeeders 14 and 16 may have an adjustable cross sectional area. Thisadjustable cross sectional area may allow different volumes of thesolids flow 22 to pass through the second seal duct 92 at differenttimes. The controller 34 may actively control the adjustable crosssectional area to maintain the desired dynamic plug 98 formed by thesolids flow 22 between the two solids feeders 14 and 16. This may beespecially useful when there is an inconsistent solid feed rate of thesolids flow 22 entering the first solids feeder 14.

Technical effects of the invention include, among other things, theability to depressurize or meter a solids flow between an upstreamsystem and a downstream system. The upstream and downstream systems mayoperate at different atmospheres, e.g., at different pressures and/orgas compositions. The multi-stage solids feeder may create one or moredynamic plugs (e.g., 1, 2, 3, or more dynamic plugs) formed by thesolids flow passing through the multi-stage solids feeder. Themulti-stage solids feeder may include one or more buffer gas supplies toaid in establishing the dynamic plugs. These dynamic plugs maysubstantially block gas from flowing through the multi-stage solidsfeeder from the upstream and downstream systems, while allowing passageof the solids flow. Buffer gas introduced to the multi-stage solidsfeeder may reduce an amount of gas that leaks from one solids feeder tothe other through the solids flow. The use of multiple solids feeders inseries may add redundancy (e.g., multiple dynamic plugs) to the system,such that any gas that leaks past one dynamic plug into one of thesolids feeders may be blocked by the next dynamic plug of the systemand/or vented out of the solids feeder. The solids feeder may bepositioned and controlled appropriately for the desired solid feedingapplication. A controller may actively control the solid feed rates ofthe different solids feeders to maintain the one or more dynamic plugs.The multi-stage solids feeder may allow more controlled metering of asolids flow between incompatible atmospheres. In addition, themulti-stage solids feeder enables controlled depressurization of asolids flow exiting a gasifier.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

The invention claimed is:
 1. A system, comprising: a multi-stage solidsfeeder, comprising: a first solids feeder comprising a first inlet and afirst outlet; a second solids feeder comprising a second inlet and asecond outlet, wherein the second solids feeder is disposed adjacent tothe first solids feeder; and a conduit disposed between the first outletand the second inlet, wherein the conduit routes a solids flow from thefirst solids feeder to the second solids feeder, wherein the systemcomprises at least one of a plurality of features comprising: themulti-stage solids feeder is configured to create a first dynamic plugof the solids flow at the first inlet, or a second dynamic plug of thesolids flow in the conduit downstream of the first outlet or at thesecond inlet, or a third dynamic plug of the solids flow at the secondoutlet, or at least two dynamic plugs of the solids flow; or themulti-stage solids feeder is configured to depressurize the solids flowfrom the first inlet to the second outlet; or the multi-stage solidsfeeder is configured to maintain a third pressure between the firstoutlet and the second inlet that is less than both a first pressure ator upstream of the first inlet and a second pressure at or downstream ofthe second outlet; or the multi-stage solids feeder is configured toreceive a buffer gas; or a controller configured to independentlycontrol a first solid feed rate of the first solids feeder and a secondsolid feed rate of the second solids feeder, or configured to controlthe first and second solids feeders to maintain at least one dynamicplug of the solids flow; or a gasifier disposed upstream of the firstinlet; or the first and second solids feeders are spaced relative toeach other such that a ratio between a minimum linear dimension from thefirst solids feeder to the second solids feeder and a maximum feederdimension of the first and second solids feeders is less thanapproximately 0.5; or the first and second solids feeders are configuredto cooperatively create at least one intermediate dynamic plug; or thefirst and second solids feeders are configured to operate at a commonoperational speed; or any combination thereof.
 2. The system of claim 1,wherein the multi-stage solids feeder is configured to create at leastthree dynamic plugs of the solids flow to substantially block gas flowwhile enabling the solids flow between an upstream system and adownstream system.
 3. The system of claim 1, wherein the multi-stagesolids feeder is configured to create the second dynamic plug of thesolids flow in the conduit downstream of the first outlet or at thesecond inlet.
 4. The system of claim 1, wherein the multi-stage solidsfeeder is configured to create the first dynamic plug of the solids flowat the first inlet.
 5. The system of claim 1, wherein the first inlet ofthe first solids feeder is coupled to an upstream system having thefirst pressure, the second outlet of the second solids feeder is coupledto a downstream system having the second pressure, the first pressure isgreater than the second pressure, and the multi-stage solids feeder isconfigured to depressurize the solids flow from the upstream system tothe downstream system.
 6. The system of claim 1, wherein the first inletof the first solids feeder is coupled to an upstream system having thefirst pressure, the second outlet of the second solids feeder is coupledto a downstream system having the second pressure, and wherein themulti-stage solids feeder is configured to maintain the third pressurebetween the first outlet and the second inlet, wherein the thirdpressure is less than both the first pressure and the second pressure.7. The system of claim 1, wherein the multi-stage solids feeder iscoupled to at least one buffer gas supply that provides a flow of thebuffer gas into a flow path through the multi-stage solids feeder. 8.The system of claim 1, comprising the controller configured to controlthe first solid feed rate of the first solids feeder and the secondsolid feed rate of the second solids feeder based on sensor feedback,wherein the controller is configured to independently control the firstsolid feed rate and the second solid feed rate.
 9. The system of claim8, wherein the sensor feedback comprises data indicative of at least oneof the first pressure upstream of the multi-stage solids feeder, thethird pressure between the first and second solids feeders, the secondpressure downstream of the multi-stage solids feeder, or a solid feedrate.
 10. The system of claim 1, comprising the gasifier coupled to thefirst inlet of the multi-stage solids feeder.
 11. The system of claim 1,comprising the controller configured to control the first and secondsolids feeders to maintain the at least one dynamic plug at the firstinlet, or between the first and second feeders, or both.
 12. The systemof claim 1, wherein the first and second solids feeders are spacedrelative to each other such that the ratio between the minimum lineardimension from the first solids feeder to the second solids feeder andthe maximum feeder dimension of the first and second solids feeders isless than approximately 0.5.
 13. The system of claim 1, wherein themulti-stage solids feeder is configured to create the at least twodynamic plugs of the solids flow.
 14. The system of claim 1, wherein themulti-stage solids feeder is configured to create the third dynamic plugof the solids flow at the second outlet.
 15. The system of claim 1,wherein the first and second solids feeders are configured tocooperatively create the at least one intermediate dynamic plug.
 16. Asystem, comprising: a multi-stage solids feeder, comprising: a firstsolids feeder comprising a first rotary mechanism disposed in a firstchamber between a first inlet and a first outlet; and a second solidsfeeder comprising a second rotary mechanism disposed in a second chamberbetween a second inlet and a second outlet, wherein the first and secondsolids feeders are disposed adjacent one another, the first outlet iscoupled to the second inlet, and the multi-stage solids feeder isconfigured to substantially block gas flow while enabling a solids flow,wherein the system comprises at least one of a plurality of featurescomprising: the multi-stage solids feeder is configured to create afirst dynamic plug of the solids flow at the first inlet, or a seconddynamic plug of the solids flow in a conduit downstream of the firstoutlet or at the second inlet, or a third dynamic plug of the solidsflow at the second outlet, or at least two dynamic plugs of the solidsflow; or the multi-stage solids feeder is configured to depressurize thesolids flow from the first inlet to the second outlet; or themulti-stage solids feeder is configured to maintain a third pressurebetween the first outlet and the second inlet that is less than both afirst pressure at or upstream of the first inlet and a second pressureat or downstream of the second outlet; or the multi-stage solids feederis configured to receive a buffer gas; or a controller configured toindependently control a first solid feed rate of the first solids feederand a second solid feed rate of the second solids feeder, or configuredto control the first and second solids feeders to maintain at least onedynamic plug of the solids flow; or a gasifier disposed upstream of thefirst inlet; or the first and second solids feeders are spaced relativeto each other such that a ratio between a minimum linear dimension fromthe first solids feeder to the second solids feeder and a maximum feederdimension of the first and second solids feeders is less thanapproximately 0.5; or the first and second solids feeders are configuredto cooperatively create at least one intermediate dynamic plug; or thefirst and second solids feeders are configured to operate at a commonoperational speed; or any combination thereof.
 17. The system of claim16, comprising the conduit disposed between the first outlet and thesecond inlet, and the multi-stage solids feeder is configured to createthe second dynamic plug of the solids flow in the conduit downstream ofthe first outlet or at the second inlet.
 18. The system of claim 16,wherein the multi-stage solids feeder is configured to create the firstdynamic plug of the solids flow at the first inlet to substantiallyblock the gas flow while enabling the solids flow between an upstreamsystem and a downstream system.
 19. The system of claim 16, wherein themulti-stage solids feeder is configured to create the first dynamic plugof the solids flow at the first inlet; the second dynamic plug at thefirst outlet, the second inlet, or the conduit between the first outletand the second inlet; and the third dynamic plug of the solids flow atthe second outlet.
 20. The system of claim 16, wherein the multi-stagesolids feeder is coupled to at least one inert buffer gas supplyconfigured to supply the buffer gas into a flow path through themulti-stage solids feeder.
 21. The system of claim 16, wherein the firstoutlet is directly coupled to the second inlet.
 22. The system of claim16, wherein the system comprises at least two of the plurality offeatures.
 23. The system of claim 16, wherein the system comprises atleast three of the plurality of features.
 24. The system of claim 16,wherein the system comprises at least four of the plurality of features.25. The system of claim 16, wherein the multi-stage solids feeder isconfigured to create the at least two dynamic plugs of the solids flow.26. The system of claim 16, wherein the multi-stage solids feeder isconfigured to depressurize the solids flow from the first inlet to thesecond outlet, the multi-stage solids feeder is fluidly coupled to thegasifier upstream of the first inlet, or a combination thereof.
 27. Thesystem of claim 16, comprising the controller configured toindependently control the first solid feed rate of the first solidsfeeder and the second solid feed rate of the second solids feeder, orconfigured to control the first and second solids feeders to maintainthe at least one dynamic plug of the solids flow, or a combinationthereof.
 28. A method, comprising: feeding a solids flow through a firstsolids feeder from a first inlet, along a first rotary mechanism withina first chamber, and out through a first outlet; feeding the solids flowfrom the first outlet through a second solids feeder from a secondinlet, along a second rotary mechanism within a second chamber, and outthrough a second outlet, wherein the first and second solids feeders aredisposed adjacent one another as a multi-stage solids feeder; andcreating at least one dynamic plug of the solids flow in the multi-stagesolids feeder to substantially block gas flow while enabling the solidsflow through the multi-stage solids feeder, wherein the method comprisesat least one of: creating a first dynamic plug of the solids flow at thefirst inlet, or a second dynamic plug of the solids flow in a conduitdownstream of the first outlet or at the second inlet, or a thirddynamic plug of the solids flow at the second outlet, or at least twodynamic plugs of the solids flow; or depressurizing the solids flow fromthe first inlet to the second outlet; or independently controlling afirst solid feed rate of the first solids feeder and a second solid feedrate of the second solids feeder; or controlling the first and secondsolids feeders to maintain the at least one dynamic plug of the solidsflow; or receiving the solids flow into the first inlet from a gasifierdisposed upstream of the multi-stage solids feeder; or any combinationthereof.
 29. The method of claim 28, wherein creating the at least onedynamic plug comprises creating the first dynamic plug of the solidsflow at the first inlet; the second dynamic plug at the first outlet,the second inlet, or the conduit between the first outlet and the secondinlet; and the third dynamic plug of the solids flow at the secondoutlet.
 30. The method of claim 28, comprising supplying at least oneinert buffer gas into the multi-stage solids feeder.
 31. The method ofclaim 28, comprising controlling the first and second solids feeders tomaintain the at least one dynamic plug of the solids flow in the conduitbetween the first and second solids feeders.